The present invention relates to the fluid processing arts. It finds particular application in conjunction with the heating and filtering of ink in ink jet printers, and will be described with particular reference thereto. However, it is to be appreciated that the present invention will also find application in the heating and filtering of fluids, gases, liquids, melting solids, evaporating solids, plasmas, particulate matter, or various combinations thereof for ink jet, electrophotographic, and other types of printing, as well as for a wide range of other fluid processing applications in the printing, medical, automotive and other arts.
An ink jet printer includes one or more printheads which apply ink droplets to paper to create printed text, graphics, images, and the like. Each printhead typically includes an ink reservoir, an ink buffer, or a fluid connection to a remote ink supply, and a tube or nozzle from which ink is ejected responsive to an applied energy pulse. In thermal ink jet printing a thermal pulse is applied to partially vaporize ink and eject one or more ink droplets. In acoustic ink jet printing, an acoustic energy pulse is applied using a piezoelectric transducer. Other approaches for effectuating the ink ejection, such as electrostatic mechanisms and microelectromechanical systems (MEMS), are also known.
Accurate control of the ink temperature is important for well controlled and reproducible ink jet printing. The ink temperature affects viscosity and other fluid properties which in turn affect the ink flow into the nozzle and the size or mass of the produced ink droplets. At cooler temperatures, ink viscosity increases and ink flow in the narrow passages of the printhead is impeded. Furthermore, when using inks which are solid at room temperature, a heating mechanism is required to liquefy or melt the ink. In the past, foil heaters have been employed to heat the ink.
Other problems can arise in ink jet printers due to particulate contaminants in the flowing ink. Such particulates can clog the nozzle or other narrow ink paths in the printhead. Another problematic ink contaminant is air dissolved into the ink. The dissolved air can accumulate into air bubbles in the printhead, producing flow blockages and printhead failure. Problems with air bubbles are particularly prevalent in isothermal chip designs. In the past, contaminant problems have been addressed by employing a porous filter arranged after the foil heater in the ink path. U.S. Pat. No. 6,139,674 issued to Markham et al. describe one such porous filter, in which the pores are formed by laser ablation in cooperation with a masking system.
The existing solutions to the heating and contamination problems have some disadvantages. The foil heater and the porous filter occupy valuable space, which can be problematic. Space in printheads is usually at a premium because it is desirable to include a large number of nozzles or ink ejectors for rapid parallel deposition of ink droplets. In addition, because the separate heater and filter elements occupy a large space, substantial energy is dissipated in the heater in order to transfer sufficient heat to the region near the filter pores. Furthermore, in carriage-type printers where the printhead moves back-and-forth across the page during printing, reduction of printhead size is advantageous. The pores of the porous filters are also susceptible to clogging by the ink during the filtering.
The present invention contemplates a new and improved method and apparatus which overcomes the above-referenced problems and others.
In accordance with one aspect of the present invention, an apparatus for filtering a substance is disclosed. An electrically insulating substrate separates a source volume containing the substance from a target volume. The substrate has a first side in fluid communication with the source volume and a second side in fluid communication with the target volume. The substrate further includes a plurality of openings connecting the first side with the second side. The openings are sized to provide filtering fluid communication between the source volume and the target volume for at least one phase of the substance. A heater film is disposed over and supported by selected portions of the substrate. The heater film contacts the substrate to heat at least a portion of the openings.
In accordance with another aspect of the present invention, an ink processing element is disclosed for use in a printhead. The ink processing element includes a substantially planar insulating substrate arranged in an ink path. The substrate has one or more porous areas that filter ink moving through the ink path. A heater film is deposited onto the insulating substrate and heats the porous areas of the insulating substrate responsive to an electrical input.
In accordance with yet another aspect of the present invention, a printhead is disclosed, including an ink reservoir containing ink, an ink jet die in fluid communication with the ink reservoir, and an ink processing element arranged in the fluid communication path between the ink reservoir and the ink jet die. The ink processing element includes a substrate having a plurality of pores formed therethrough. The pores are sized to provide a selected filtering of ink passing between the ink reservoir and the ink jet die via the pores. The ink processing element further includes a heater film integrated with the substrate to form a planar ink processing element. The heater film is deposited on the substrate and patterned to define a selected heater shape.
In accordance with still yet another aspect of the present invention, a method is provided for fabricating a substance-processing element. Openings are defined through an insulating substrate. The openings are sized to provide a selected filtering of the substance, and are arranged to define porous filtering areas. A resistive heater film is deposited over selected areas of the substrate to define a foil heater that heats at least the porous filtering areas responsive to an electrical input.
Numerous advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.